Old Res Weather

Lexington, Massachusetts, USA

35°F

2/16/2025 7:17pm

Lexington Conditions: Few Clouds
Temperature: 35.1°F / 1.7°C
Dew Point: 32.4°F
Relative Humidity: 90%
Wind: Calm, 10-min avg: Calm, gust: None
Barometer: 29.00 in Falling Slowly
Visibility: 10 miles
Rain Today: 0.01 in
UV Index: $VPuv None

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 242252
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
652 PM EDT Fri Jul 24 2026

.WHAT HAS CHANGED...

The chance for rain for the Cape and Islands on Sunday has decreased 
since the last forecast update. Potential exists for heavy 
rainfall and perhaps even the risk of localized flash flooding 
beginning late Monday into the middle of next week.

&&

.KEY MESSAGES...

- Pleasant and dry conditions expected through Monday except 
  for far eastern MA, the Cape and Islands. Elevated rip 
  currents possible for east facing beaches Sunday. 

- Periodic chances for showers & t-storms late Mon-Wed perhaps 
  lingering into Thu...heavy rain/localized flash flood risk.

&&

.DISCUSSION...

KEY MESSAGE 1...Pleasant and dry conditions expected through Monday 
except for far eastern MA, the Cape and Islands. Elevated rip 
currents possible for east facing beaches Sunday. 

Another cool night ahead as clear skies support radiational cooling. 
Thus, opted to blend in the NBM 10th percentile and MOS guidance for 
lows tonight. Lows range from the upper 40s across elevated portions 
of the interior, to near 60 in urban and coastal areas. High 
pressure moves offshore Saturday switching winds to the E with low 
relative humidity values. Expecting another dry and pleasant day 
with Highs across the interior likely range in the low to mid 80s 
while the onshore flow will keep temperatures slightly cool (mid-
upper 70s) along the immediate eastern coastal areas.

By Sunday, heights fall as a weak trough approaches from the west. 
Most guidance shows a weak surface low tracking along a boundary 
well to the S of the region Sunday afternoon. Compared to the last 
forecast update, the NAM has backed off on the more robust POPs 
associated with a push of moisture across the Cape and E MA Sunday 
afternoon.  Model soundings still indicate a shallow layer of 
moisture in the lower levels supported by the easterly surface flow 
with drier mid-level air. This could potentially point to a layer of 
low clouds and even some patchy drizzle in areas of eastern MA 
developing through the day on Sunday. 

Outside of limited precip chances, there is higher confidence in a 
period of elevated rip current risk developing on Sunday with 
increasing easterly flow. Greatest threat for rough surf and rip 
currents will likely be across much of the east-facing portion of 
the Cape, MA, and the Islands. 

KEY MESSAGE 2...Periodic chances for showers & t-storms late Mon-Wed 
perhaps lingering into Thu...heavy rain/localized flash flood risk.

The next shortwave trough approaches the region from the west in the 
late Mon-Wed timeframe. This will allow southerly flow to bring 
typical summerlike humidity back to southern New England. This will 
also bring a return to period chances of showers and thunderstorms 
to the region in the late Mon-Wed time frame...perhaps lingering 
into Thu if the shortwave is slower to depart. While there is quite 
a bit of spread in regards to timing and track...the ECMWF/GFS/UKMET 
indicating the potential for an approximately 995 mb surface low. 
That is pretty anomalous for July standards and the EPS ensemble 
situational awareness table indicates its strength outside the 
models climatology field. Pwats are also indicated to increase to 1+ 
standard deviation above normal on the order of 1.5 to 2". When you 
combined that with the potential for a 995 low pressure system...the 
potential is certainly there for a heavy rain/localized flash flood 
risk. And that may not even end up in our region depending on the 
track...But it certainly bears watching for the mid-Atlantic and 
northeast states. 

We also should mention that the late Mon through Wed timeframe will 
not be a complete washout. Timing obviously uncertain at this 
point...But afternoons/evenings are favored given diurnal 
instability to work with as well. 

Temperatures fairly seasonable for this time of year. Lows may be a 
bit above normal with highs a touch below normal given the 
increasing low level moisture  and precipitation chances for the 
middle of next week.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
Forecaster Confidence Levels...

Low - less than 30 percent. 
Moderate - 30 to 60 percent. 
High - greater than 60 percent.

00z TAF Update...

Tonight through Saturday...High confidence.

VFR. Light/calm winds tonight become ESE 5-12 knots on Sat. 

Saturday night...High confidence.

Mainly VFR but some MVFR cigs/vsbys may impact parts of RI/SE MA
toward daybreak Sunday. Greatest risk across parts of the Cape
and Nantucket. Calm/light NE winds.

KBOS Terminal...High confidence in TAF. Sea breeze will kick 
back out to the light S/SSW 00-02z. Easterly winds between 6 
and 12 knots redevelop by 13z/14z Sat.

KBDL Terminal...High confidence in TAF.

Outlook /Monday through Wednesday/...

Monday: VFR. Breezy. 

Monday Night: VFR. Chance SHRA, slight chance TSRA.

Tuesday through Tuesday Night: Mainly VFR, with local MVFR
possible. Breezy. SHRA likely, slight chance TSRA.

Wednesday: Mainly VFR, with local IFR possible. Breezy. Chance
SHRA, slight chance TSRA.

&&

.MARINE...
Forecaster Confidence Levels...

Low - less than 30 percent. 
Moderate - 30 to 60 percent. 
High - greater than 60 percent.

Through Saturday...High confidence.

Light winds and seas 1-4 ft Saturday. Increasing winds and seas
Saturday night and Sunday with a low chance of SCA conditions
across the eastern outer waters Sunday. 

Moderate risk for rip currents over the weekend.

Outlook /Monday through Wednesday/...

Monday through Monday Night: Winds less than 25 kt. 

Tuesday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain showers. 

Tuesday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of seas approaching 5 ft. Rain showers
likely, slight chance of thunderstorms. 

Wednesday: Winds less than 25 kt. Seas up to 5 ft. Chance of
rain showers, slight chance of thunderstorms.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.

&&

$$

DISCUSSION...FT/Frank
AVIATION...FT/Frank
MARINE...FT/Frank